Problems with the existing art in brushless DC motors include an inherent torque reduction at the time of commutation, friction and magnetic cogging which acting together are referred to as "torque ripple". Most commonly, a three-phase brushless DC motor utilizes only six commutation points per 360 electrical degrees and is driven by three signaling devices, such as hall sensors.
One solution to the problem of torque ripple has been the use of sinusoidal current drive systems. However, these are extremely expensive and require a high accuracy shaft angle detector physically built into the motor structure followed by a large amount of accompanying electronic circuitry.
It is known to utilize 12-step commutation in a three-phase stepper motor to achieve twelve torque-producing steps within each 360 electrical degrees U S. Pat. No. 3,621,358 to Hinrichs et al, which is hereby incorporated by reference, discloses such a wiring circuit which is driven by a clock pulse generator connected to a shift register and logic gates producing a stepper motor with twelve steps per every 360 electrical degrees.